IS 6855:2003

Indian Standard METHOD OF SAMPLING FOR LIQUID DIELECTRICS (First Revision) ~:

ICS 29.040.10

0 BIS 2003 BUREAU MANAK OF BHAVAN, INDIAN STANDARDS ZAFAR MARG

9 BAHADUR SHAH NEW DELHI 110002

October 2003

Price Group

5

Fluids for Electrotechnical

Applications

Sectional Committee,

ET 03

FOREWORD This Indian Standard (First Revision) was adopted by the Bureau of Indian Standards, after the draft finalized by the Fluids for Electrotechnical Applications Sectional Committee had been approved by the Electrotechnical Division Council. The standard was first published in 1973. This revision has been necessitated users concerning the practical aspects of this standard. on receiving the comments from the

While testing liquid dielectrics, it is essential that correct sampling procedure is followed for drawing reliable conclusions from the test. This standard has, therefore, been the general principles for sampling of liquid dielectrics from the new supplies as wellas from the equipment in service. The general principles covered in this standard apply to liquid dielectrics whose kinematic viscosity at 40"C is less than 500 mm2/s (Cst). Particular standards are to be referred to, if the kinematic viscosity is greater than analysis mm2/s (Cst) at 40°C specific provisions may also be referred to for drawing of samples of insulating oils from transformers in service for the purpose of dissolved gas analysis. This standard does not purport to address all of the safety concerns of handling of the liquid dielectrics being sampled as well as other material used for cleaning the sampling devices. It also does not cover the handling and disposal of samples and containers to prevent environmental contamination. In the preparation of this standard assistance has been derived from the lEC Document 10 (Central Office)216 `Sampling method for liquid dielectrics, issued by the International Electrotechnical Commission and the method D923 `Standard practices for sampling electrical insulating liquids', issued by the American Society for Testing and Materials For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with IS 2:1960 `Rules for round in: off numerical values (revised)'. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

IS 6855:2003

Indian Standard METHOD OF SAMPLING FOR LIQUID DIELECTRICS (First Revision)
1 SCOPE 1.1 This standard describes the procedures to be followed for sampling new liquid dielectrics in their delivery containers, as well as insulating liquids in service in transformers and switchgear. 1.1.1 This standard applies only to liquid dielectrics whose kinematic viscosity at 40"C is less than 500 mm2/s (Cst). 2 REFERENCES The following standard: IS No. 1745:1978 Specification hydrocarbon revision) standards are necessary adjuncts to this 4.1 New Liquid Dielectrics 4.1.1 Sampling Point As physical contaminants like solid particles and water are not ordinarily dispersed uniformly through the liquid being sampled, it is necessary to draw samples from specific locations in the container where contaminants could predominate. For a liquid having relative density (specific gravity) of less than one to be found at the bottom, whereas in case of a liquid having specific gravity greater than one (for example Askarels), some of these impurities are most likely to be found on the surface. To evaluate the representative quality of consignment, three types of samples may be taken (see 3.2 to 3.4).
NOTE -- If from the same lot, individualsamples are drawn fromdifferentcontainers(for example, in the case of drums), the tests need to be carried out on composite samples,

Title for petroleum solvent (second sampling

4.1.2 Rail Tankers and Road Tank Wagons Samples shall be from in 4.1.5.2. the following 4.1.2.1 Drums Samples should be taken as described in 4.1.5.3. Test shall be conducted separately on each lot for ascertaining its conformity to the requirements of the specification. The number of drums to be selected at random from a lot for this purpose shall depend on the size of the lot and shall be as given below: Selection of Samples from Drums No. of Drums in a Batch 2to 5 No. ofDrums @om Which Samples to be Taken 2 3 4 7 each tanker as described

4905:1968 3 TERMINOLOGY

Methods for random

For the purpose of this standard, definitions shall apply. 3.1 Sampling

A practice for obtaining that amount of material which is adequate for conducting the required tests and which is representative of that portion of the liquid fi-om which it is taken. 3.2 Average Sample levels from a

Mixture of samples drawn at different single container. 3.3 Individual Sample

Sample or mixture of samples drawn from the same level from a single container. 3.4 Composite Samples

6to 20 21to 50 61to 100 lolto 200 201 to 400 401 and more

10
15 20

Mixture of-samples drawn from the same level from several identical containers. 3.5 Lot All the containers of the same capacity and constituting single batch of manufacture shall constitute a lot. 4 GENERAL PRINCIPLES FOR THE SAMPLING OF LIQUID DIELECTRICS

NOTE -- For ensuring randomness, use of suitable random number tables given in IS 4905 is recommended. In case such tables are not available, the following procedure may be adopted: `Starting from any drum, count them as 1,2, .. ... ... up to r and so on, in one order, where r is the integral part of N/n (h'being the number of drums in the lot and n being the number of drums to be selected). Every # container thus counted shall be withdrawn to give the sample for tests.'

[S 6855:2003 4.1.3 Quantily of Sample to be Taken 4.1.4.3 Sampling equipment Four types of sampling equipment have been described under two heads depending on the container fi-om which the sample is to be drawn as given below: Sampling from rail tankers and road tank wagons -- The thief dipper shown in Fig. 1 is suitable for taking sample from the bottom of the container. This dipper is made from stainless steel or aluminium tubes and castings with machine-finished al~over. It shall be suflkiently heavy to sink in the liquid. The cream dipper shall be used for taking samples from top surface of the liquid dielectrics. This device shall be constructed as shown in Fig. 2 and shall be of stainless steel. Sampliwg from drums-- For this purpose, the pipette shown in Fig. 3, which enables sample to be taken from any level in the drums shall have a capacity of about 500 ml. Another device suitable for drawing samples from drums containers from the required level is the Siphon pressure thief as shown in Fig. 4. It consists of two tubes; one (internal diameter 13 mm) meant for applying air pressure is made of metal. Both tubes are set in a bung whose dimensions correspond to the diameter of the bung hold in the drum/container. The cream dipper (see Fig. 2) may also be used for taking top samples (see 4.2.2 of liquids in drums/ containers). 4.1.4.4 Sample containers

This depends on the nature of the liquid dielectric being exam ined and the test performed to ascertain the quality (.yee 5). 4.1.4 Sampling 4.1.4.1 Equipment

General precautions

Since the results of the tests prescribed for liquid dielectrics can greatly depend on the possible impurities in the sample, it is essential to observe the following precautions: a) All sampling equipment (sampler and containers) should be reserved exclusively for each type of liquid (for example oils, askarels, silicone fluids, etc). b) The equipment and shall be perfectly clean and dry;

c) The equipment shall, preferably, be made of glass, although stainless steel and aluminium are also suitable. Other equipment may also be used provided it does not introduce contaminants in the samples. 4.1.4.2 Cleaning of sampling equipment and containers Particular attention should be paid to ensure the absence of any traces of solid impurities, such as dues, fires, etc. The use of rags or any fibrous material for cleaning is not permitted. Glass equipment shall be first cleaned with a solvent and after that it shall be cleaned with concentrated sulphuric acid, then rinsed copiously with tap water followed by distilled or deionized water, until the rinsings have a neutral reaction. Metal equipment shall be cleaned twice with a solvent.

Various types of containers maybe used according to the nature of the liquid to be sampled. Table 1 indicates the recommended options. The containers shall be so stoppered as to allow them to be sealed. Glass .containers are stoppered either by means of cork stopper wrapped in aluminium or by ground-glass stoppers and metallic containers by a double closure (Polytetrafluorethy lene sealing capsule and screw stopper). Rubber stopper and/or seals shall not be permitted. Each container shall have a label on which are marked all the indications necessary to identify the contents, such as corresponding markings of the drums or tanks, date and purpose of sampling and the names of the drawing agency and the consignee laboratory. 4.1.5 Sampling Procedure 4.1.5.1 Precautions

After cleaning, the equipment is drained and dried in an air oven at 105 to 110°C. After drying, it should be immediately protected from contamination and not opened until just before use. Equipment too long to be accommodated in an oven, is rinsed successively with acetone and ether and then dried by blowing warm air through it. 4.1.4.2.1 Nature of solvent to be used

a ) For mineral insulating oils -- Petroleum solvent without additives (boiling point below 80°C) may be used. Solvent 60/80 grade of 1S 1745 is considered suitable. b) For askarels -- Trichlorofluoromethane, carbon tetrachloride or some suitable solvent not derived from a petroleum base may be used. (This is because askarels may be subjected to the oilcontamination and traces of petroleum base solvents may affect the thermal stability test results). 2

Every precaution shall be taken, when sampling so as not to contaminate the liquid dielectric with dirt, dust fibrous matter or moisture. Outdaor sampling of dielectric liquids in rain, fog or high wind should be

IS 6855:2003 Tablel Types of Containers and 5.1 .3)
[Jsed Hydrocarbon

(Ckwses 4.1.4 .4,5.1.2
S[ No. Container c--------~ Askarels (i) i) ii) iii) iv) a) b)
I) Care

Product Type Hydrocarbon Oils (4) Yes Yes No Yes

(2) Amber glass bottle Drawn aluminium bottles Metallic soldered bottles Clear, inactinic glass bottle2)

(3) Yes Yes No Yes

(5) Yes Ycs Yesl) Yes

NOTE-- Volume of the containers shall be a..follows: Containers for the individual samples--The containers shall have a capacity of one or two Iitres. Container for the mixing of average or composite samples-A
is needed bottles in the are use

container with capacity of at least six Iitres is necessary.

of soldered bottles as interaction between oil and some soldering materials may occur.

z) If

clear

used, they shall not be exposed to light for more than 5 minutes at any time after sampling.

avoided and is only permitted if all the precautions have been taken to avoid pollution of the liquid. In this case, the use of special covers is necessary. Condensation shou Id be avoided by warming the sampling equipment so as to be above the ambient air temperature. Before use, the equipment should be rinsed with the liquid being sampled. During all these operations, every care should be taken to avoid contaminating the liquid dielectric. The operator shall be warned not to permit his hands to come in contact with the sample or the internal surface of flasks and of other sampling equipment. The liquid dielectric samples shall be protected against all kinds of light radiation during transportation and storage. On arrival at the laboratory, the sampling bottles shall not be opened immediately. lt is necessary to wait till the temperature of the sample is in equilibrium with the room temperature. 4.1.5.2 .Vumpling from wa<qon.s rail tankers and road tank

Allow the oil to trickle slowly through the valve so as to remove the impurities and stagnant oil in the valve and associated pipe work. After about ten Iitres have been removed or the oil has run for 4 to 5 rein, run a quantity of oil into a sample container for rinsing. Rinse the sampling container with the liquid dielectric. b) Fill the bottle with the sample. c) Sampling with a thief dipper or a cream dipper-- Sampling with a thief dipper or cream dipper should be done only after the tank has been allowed to stand for at least one hour after the vehicle has arrived.
NOTE -- It is also possible, by this procedure, to obtain the equivalent of an average sample, if the sampling is done immediately after the vehicle has arrived.

Dielectric liquid may be sampled either through the sampling valve at the tank outlet or by means of the thief dipper or the cream dipper. Sampling through-the tank outlet -- By this procedure, it is possible to obtain a representative sample from the bottom of the tank. The sample should be drawn after the vehicle has been allowed to stand for at least one hour from the time of its arrival.
NOTE -- [t is also possible, by this procedure, to obtain the equivalent of an average sample, if the sampling is done immediately after the vehicle has arrived. [II this case, the sampling procedure shall be as follows:

d) Procedure with the thief dipper (see Fig. I ) (bottom samples) --For taking bottom samples (that is, within 13 mm from the bottom of the tank) the dipper is lowered till the projecting stem of the valve rod strikes the bottom of the tank. The dipper then tills; tilling is complete when no more air bubbles, escape. The dipper is then withdrawn and its contents poured into a sample container (in the case of an individual sample) or more usually a glass mixing container for mixing the various samples taken (in the case of a composite or average sample). In the latter case, the total volume collected is distributed among the sample containers.
NOTE --The dipper should always be suspended by means of clean metal wire or chain ropes, strings or other tibrous materials shalt not be used,

a) Remove the outlet valve shield, if fitted. Remove all visible dirt and dttst from the valve by means of iint-free clean cloth. The outlet system (pump, delivery pipe), if incorporated, shall be started or opened as appropriate in order to get a sample. 3

Procedure with the cream dipper (see Fig, 2) (top samples) -- With this device, the sampling procedure shall be as follows: With the valve closed, fill the dipper by slowly

[S 6855:2003 HOOK FOR METAL OR WIRE
CHAIN

T
100

&

All dimensions

in millimetres.

FIG. 1 THIEF DIPPER

immersing it in the liquid to be sampled until the rim is just below the surface of the liquid so that it shall flow slowly into the dipper. Discard the first filling. Refill the dipper as above and transfer the sample to the container by allowing it to flow from the bottom orifice against the side of the container and not in a stream into the bottom of the container. Repeat the operation until sufficient liquid has been obtained to fill the sample container (individual sample) or the mixing container (composite or average sample). 4.1.5.3 .Tamp[e from drums

top, protected from dust or rain. The bung area and top surface of the drum shall be cleaned with lint free dry cloth before opening. The pipette (see Fig. 3) or the syphon pressure thief (see Fig. 4) is used. The cream dipper (for taking a sample from the surface layer of the liquid) may also be used. a) Procedure with a pipette:

1) Block the upper orifice of the pipette with the thumb, and then immerse the pipette in the liquid to the required depth. 2) Remove the thumb to allow liquid to enter the pipette. 4

Sanlple should be taken only after the drums have been allowed to stand for at least 8 h with the bung intact on

IS 6855:2003

T
St 1

406

1
127 1
All dimensions in millimetres. FIG.

2 CREAM DIPPER 5) (Composite or average sample) taking care not to form air bubbles during pouring of the liquid. c) Procedure with a cream dipper -- see 4.1.5.2. 4.1.6 Sampling Report The sampling report should give all the information necessary for identi@ing the sample as well as any details or special information likely to be of help to those entrusted with the test. The type of sample (that is, composite, individual or average sample) should be specified. It is also necessary to state the ambient temperature and humidity at the time of sampling. This is required to ascertain if any pre-treatment of the samples is required before conducting the electrical test. A copy of the report should accompany each sample. The distribution of samples shall be done in accordance with the procedure as agreed to between the supplier and the purchaser. 5

3) Again close the upper end of the pipette with the thumb and -withdraw the pipette. 4) The first content is used for rinsing, transfer the next filling into either .a sampling Individual sample or a mixing container (composite or average sample) taking care not to form air bubbles during pouring of the liquid. b) Procedure with a syphon pressure thiej

1) Fit the bung carrying the riser and the pressure tubes into the bung hole of the drum and ensure that this seal is air-tight. 2) Adjust the lower ends of the tube to the desired level. ~) Raise the pressure inside the drum by means of the rubber bulb. 4) Run off enough liquid to rinse the tube and then draw off the required quantity directly into the sampling (individual sample) or mixing container.

IS 6855:2003 4.2 Liquid Dielectrics Point
preferably, be carried out

in Service

4.2.2 General Precautions The following general precautions shall be taken:

4.2.1 Sampling
Sampling shall,

while the equipment is operating normally. This requirement is particularly necessary when water content and other characteristics depending on it, are to be checked. The manufacturer's instructions for taking samples of liquid dielectric shall be followed and particular attention paid to the safety precautions to be taken. In absence of any further indication, only the raiding (for insulating oils in transformers and switchgear) and refilling (for askarels in transformers) orifices shall be used. The temperature of the liquid at the time of sampling shall be recorded.

a) Use only clean dry containers. b) Take samples preferably in dry weather and avoid any external contamination (if weather is bad, -special precautions shall be taken) (see 4.1.4.1). c) If possible, the liquid dielectric shall beat least as warm as the ambient air. d) Do not draw samples from any energized electrical equipment with a small volu~e of the liquid. In case of instrument transformers or similar equipment with small liquid

965

GLASS TUBING TAPERED AT BOTH ENDS

40

1

1

w"
All dimensions in millimetres.

FIG. 3 PIPETTE

6

IS 6855:2003 AIR BULB 7

SAMPLE

BOTTLE

GLASS TUBE 130 BORE

------------------QJ
OR -------`== ----- = --------------=-. --, -t3
All dimensions in millimetres.

CONTAINER

FIG.

4 SYPHON PRESSURE THIEF samples of new mineral oils should be taken from the bottom of the container where contamination is likely to be the greatest. But in certain cases, an average sample is also of interest. The different cases have been given in Table 2.
NOTE -- In special circumstance, it may be of interest to take sample from intermediate levels in tanks or Iarge.drums. The procedure to be followed for sampling at the intermediate levels shall be given in Annex A. 5.1.2

volume, the manufacturer's instruction on sampling procedure and quantity shall be followed. 4.2.3 Sampling Procedure

a) Be sure that the sampling done by an experienced person. Unrepresentative samples are often obtained when sampling from electrical equipment with sampling ports mounted on drain valves without adequate preparation. The flow allowed by these valves/ports is so adequate to proper flush the line from contaminants
accumulated during dormancy. It is necessary

Type of Recommended

Sampling Bottle

See Table 1. Ensure that each of the sampling bottles is filled to 95 to 98 percent of its capacity.
NOTE -- Before sampling from the transport tankers or the tank wagons sufficient oil shall be pumped from the end of the delivery pipe, as required by 4.1.4.2,

to clean these to be-free from-dirt and moisture prior to drawing the sample.
b)

First run off a sufficient quantity of liquid (at least one litre) to eliminate any contaminants which might have accumulated in the drain cock. with the liquid being

5.1.3 Mineral Insulating Oils in Service The general sampling procedures shall be as described in 4.2, samples from the tanks of all types of transformers shall be taken from the bottom of the tank, either from the drain cock provided for this purpose or from the lower drain cock, preferably at operating temperature. The quantities of oil to be taken for carrying out routine tests for maintenance purposes areas follows: Test Tests on site Laboratory tests Quanti~ of Oil

c) Rinse the containers sampled.
d)

After taking the sample, ensure that the cock is correctly closed. Check that the label markings complete. Store samples in a dark place. Fill the containers by allowing the liquid being sampled to flow against the side of the containers, thus avoiding entrapment of air. every care should be taken to
dielectric. contaminating the liquid

e)

are correct and

f) ~)

At least two litres Three litres

During these operations,
avoid 5

For type of container, see 4.1.4.4 and Table 1. 5.2 Askarels 5.2.1 General Considerations

SPECIAL

PRECAUTIONS Oils Oils for sampling (see 4.1.1),
7

5.1 IVliner-al Insulating

5..1.-1 New Mineral Insulating
According to general principle

5.2.1.1 Safety Askarel may be irritating to skin. All possible care

1S 6855:2003 should be taken to avoid breathing contact with the skin. 5.2.1.2 Sampling askarel fumes or 5.2.2.2 Type of recommended sampling bottle

See Table 1. Ensure that each of the sampling bottles is filled to 95 to 98 percent of its capacity. 5.2.3 Askarels in Service 5.2.3.1 Sampling The general procedures in 4.2.1. shall be followed as described

Unless otherwise specified, askarel samples shall be taken from the surface layer of the liquid. 5.2.1.3 Spillage

Utmost care is required for avoiding any spillage in order to prevent environmental contamination. 5.2.2 New Askarels 5.2.2.1 According to general principles for sampling (see 4.1 .1), samples of new askarel shall be taken from the top level where contamination is likely to be the greatest. But in certain cases, an average sample is also of interest. The different cases have been given in Table 3.
NOTE -- In special circumstances, it may be of interest to take samples at intermediate levels in tanks or drums. Examples of procedure are given in Annex A.

a) Sealed transformers with gas blankets and open breather type transformers -- Samples from the tank of transformers should be taken from the sampling outlet located at or near the liquid level point so that atop sample of the liquid maybe obtained. b) Conservator-type transformers completel>~filled with askarels -- Samples from the tanks of transformer shall be taken from the bottom.

Table 2 Sampling of New Askarels (Clause 5.1. 1)
Type of Delivery (1) Recommended (2) Sampling Sampler to be Used (3) Procedure (Ref to Clause of Tbis Standard) (4)

Drums

Composite Individual

Pipette (see Fig. 3) Syphon (see Fig. 4) Thief dipper (see Fig. 1) or None (Valve)

4.1.5.3(a) 4.1.5.3(b) 4.1.5.2(b) 4.l,5,2(a)

Rail tankers, tank wagons

Composite Average

Table 3 Sampling of New Askarels (Clause 5.2.2. 1)
Type of Delivery Recommended Sampling Sampler to be Used Procedure (Ref to Clause of Tbis Standard)

(1)

(2) Composite / Individual Composite / Individual

(3) Cream dipper (see Fig. 2) Cream dipper (see Fig. 2)

(4)
4.1,4.3 4.1.5.2 (a) 4.1.5.2 (b)

Drums Rail tankers, tank wagons

8

IS 6855:2003 ANNEX (Clauses PROCEDURE A-1 USE OF THE PIPETTE A-1.1 See Fig. 3 and 4.1.4.3. The pipette is immersed to the required depth. A-2 USE OF THE SYPHON A-2. I See Fig. 4 and 4.1.4.3. to the required depth. The siphon is immersed 5.1.1 A

and 5.2.2. 1)
AT INTERMEDIATE LEVELS

FOR SAMPLING

displacement of the rod does not exceed 50 mm. The dipper then shall fill. Filling shall be complete when no more air bubbles escape. The sampler is then withdrawn and its contents poured into a sample container. A-3.2 The dipper shall always be suspended by means of a metal wire or chain: string or other fibrous materials shall not be used. A-3.3 The samples taken at intermediate levels for making the average sample are transferred to an appropriate container as soon as they are drawn. The average sample is then transferred to fill the sampling bottles.

A-3 USE OF THE THIEF DIPPER A-3.1 See Fig. 1. The dipper suspended by the chain attached to the handle shall be allowed to sink to the required depth. The chain attached to the central rod shall be pulled, care being taken that vertical

9

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of Indian

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from Dot: No. ET 03 (5329). Issued Since Publication Text Affected

Amendments Amend No.

Date of Issue

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